RESUMO
A 58-year old man was referred to our hospital for treatment of an abdominal mass. As for him, tumor resection with right nephrectomy had been performed ten years ago for a giant well-differentiated perinephric liposarcoma. CT examination showed a huge tumor shadow in the abdominal cavity. Abdominal MRI examination showed a 15 × 8 cm tumor with almost high signal intensity on the T2 weighted images. At laparotomy, a large bulky retroperitoneal tumor pointed out before an operation was found. Surgical extirpation of the tumor was performed. Besides, several tumors of the thumb head size were detected into right retroperitoneal fatty tissue. The right side mesocolon and the tumors were not able to exfoliate, therefore right hemicolectomy was performed. Histological features showed dedifferentiated liposarcoma. The postoperative course was uneventful. But eight months after surgery, he was admitted again for treatment of a 4 × 3 cm retroperitoneal tumor. Extirpation of the tumor was performed. Histological finding of this tumor also showed dedifferentiated liposarcoma. Dedifferentiation, occurring in 15% of the well-differentiated liposarcomas, sometimes may develop later. Long-term detailed follow-up is necessary for well-differentiated liposarcoma.